1. Field of the Invention
The present invention relates to a slim type fingerprint recognition device using a contact light emitting device and a thin film transistor (TFT) fingerprint input device.
2. Description of the Background Art
A general fingerprint recognition device is roughly classified into an optical type using a lens or prism and a chip-based sensor using a semiconductor application technology, but the chip-based sensor gets an advantage over the other sensors. In a forthcoming mobile commerce era, an authentication sensor needs to be slim and simple. Accordingly, the present invention suggests a slim type fingerprint recognition device by using a contact light emitting device and an amorphous image sensor.
A fingerprint recognition device using a contact light emitting device and a complementary metal-oxide semiconductor (CMOS) and a plane TFT fingerprint recognition device using photosensitivity of amorphous silicon (a-Si:H) are explained as conventional arts of the present invention.
Although not illustrated, a method for forming a touch pad by using a TFT fingerprint input device and a touch pad having a fingerprint input function have been applied for registration in order to solve structural problems of a portable computer by integrating a fingerprint input device of FIG. 2a discussed later and a conventional touch pad and LCD display window (Korean Patent Unexamined Laid-open Publication No. 2001-0083355, Sep. 1, 2001). However, the aforementioned technology provides a touch pad function to the conventional fingerprint recognition device, but does not mention improvement in fingerprint recognition performance of the fingerprint recognition device.
On the other hand, FIGS. 1a and 1b are views illustrating the construction of the fingerprint input device using the CMOS and the contact light emitting device, FIG. 2a is a cross-sectional view illustrating a basic TFT fingerprint input device, and FIG. 2b is a cross-sectional view illustrating a light sensing unit of the TFT fingerprint input device.
The operation of the conventional fingerprint input device will now be explained with reference to the accompanying drawings. As illustrated in FIGS. 1a and 1b, when a user contacts his/her fingerprint to the contact light emitting device 1, a fingerprint image emits light on a contact surface. The fingerprint image is collected through a lens 2 and transmitted to a CMOS image sensor 3 for recognition.
Referring to FIGS. 2a and 2b, in an LCD panel produced by TFT-LCD companies, a TFT-array substrate of a lower plate and a back-light are used except for an upper plate which is a color filter portion. Here, the device senses light reflected by a fingerprint and recognizes an image by using a photo-current, instead of using the optical system of FIG. 1a. 
A photoresist layer 9c such as a-Si:H is formed between a drain electrode 9a and a source electrode 9b of the light sensing unit 9. When light is incident on the photoresist layer 9c over a predetermined light amount, the drain electrode 9a and the source electrode 9b are electrically connected. Therefore, when the fingerprint touches the TFT fingerprint input device 5, light generated from the back light below a transparent substrate 6 is reflected in fingerprint patterns, and received by the photoresist layer 9c of the light sensing unit 9, thereby electrically connecting the light sensing unit 9. Reference numeral 9d denotes a gate electrode of the light sensing unit 9.
On the other hand, a switching unit 8 is switched in every frame set up to scan fingerprints according to a gate control signal applied to a gate electrode 8d, for forming the fingerprint image inputted to the TFT fingerprint input device 5 as the frame scanned in each aligned light sensing unit 9. Accordingly, a light shielding layer 8c covers a drain electrode 8a and a source electrode 8b to protect the switching unit 8 from external light.
As described above, as shown in FIG. 1a, when the fingerprint input device is embodied in a bulk type by using the CMOS image sensor 3, not the TFT, a price and size of the device are increased.
In addition, also referring to FIG. 1a, light generated by the contact light emitting device 1 is separated from the CMOS image sensor 3, and thus the optical image of the fingerprint becomes dim in the sensor due to light loss, thus reducing image quality.
In the conventional TFT fingerprint input device, an effective sensing area of the photoresist layer 9c of the light sensing unit 9 is as large as an area of the photoresist layer 9c exposed between the drain electrode 9a and the source electrode 9b. However, a real incidence area of the fingerprint reflection light incident on the light incidence layer is much wider than that. That is, the light reflected by the fingerprint reaches the photoresist layer 9c after dispersion, and thus is incident at a wide angle. Especially in a structure where a plurality of light sensing units 9 are aligned, when the fingerprint is inputted to the real incidence area positioned between the adjacent light sensing units 9, resolution of the fingerprint pattern is deteriorated.
Differently from the optical type using the lens 2 and prism, the non-lens TFT which is the plane fingerprint recognition device cannot easily reduce the real incidence area through the lens 2 or prism.
Accordingly, it is a primary object of the present invention to provide a slim type fingerprint recognition device by using a contact light emitting device and a TFT fingerprint input device.
Another object of the present invention is to provide a fingerprint recognition device which can reduce a real incidence area to be equalized to an effective sensing area by using a contact light emitting device of a TFT fingerprint input device and the TFT fingerprint input device.
In one aspect of the present invention, to achieve the above-described objects of the invention, there is provided a slim type fingerprint recognition device including: a TFT fingerprint input device having a structure where a plurality of unit cells including an light sensing unit and a switching unit are aligned; and a contact light emitting device being installed on the TFT fingerprint input device, the TFT fingerprint input device and the contact light emitting device being adhered to each other by an adhesive layer, one alternating current terminal being connected to a transparent electrode layer of the contact type light emitting device.
In another aspect of the present invention, there is provided a slim type fingerprint recognition device using a contact type light emitting device and a TFT fingerprint input device, including: the TFT fingerprint input device (amorphous image sensor) having a structure where a plurality of unit cells including an light sensing unit and a switching unit are aligned; and the contact light emitting device installed on the TFT fingerprint input device, wherein the contact light emitting device includes: a transparent electrode layer directly deposited on the TFT fingerprint input device in a thin film type, one alternating current terminal being connected to the transparent electrode layer; a light emitting layer formed on the transparent electrode layer; a light shielding layer formed on the light emitting layer; a dielectric layer formed on the light shielding layer; and a water repellent layer (abrasion-resistant film) formed on the dielectric layer.